In vehicles currently available urea, for example, is used as a reducer in SCR systems (where “SCR” is an abbreviation for “selective catalytic reduction”), the system comprising an SCR catalytic converter, in which the reducer and NOx gas can react and are converted to nitrogen gas and water. Different types of reducer can be used in SCR systems. One commonly used reducer is, for example, AdBlue.
One type of SCR system includes a container that contains a reducer and a pump configured to pump the reducer from the container through a suction pipe and to supply it through a pressurised pipe to a dosage unit arranged at an exhaust system on the vehicle, for example, at an exhaust pipe at the exhaust system. The dosage unit is configured to inject a required amount of reducer into an exhaust system upstream of the SCR catalytic converter. The required component is selected according to drive routines that are stored in a control unit in the vehicle.
There is a need to reduce the amount of emissions from engines in motor vehicles. This applies not least for heavy motor vehicles such as trucks and buses, since legal requirements for ever-lower emissions are continuously being tightened.
Application of an exhaust brake at an engine of a motor vehicle during starting of the engine, such as during the cold start of the engine, is currently known, in order in this way to achieve a more rapid warming of the engine and a post-treatment system.
During the start, such as during the cold start, of a motor vehicle a yellowish or brownish smoke sometimes may initially be exhausted to the surroundings of the vehicle through an exhaust passage from the engine. The feed out of smoke may in certain circumstances continue for several minutes. This smoke is undesired for several reasons. Not only can the smoke negatively impact the environment, but it also can create a negative impression of the performance of the vehicle. Furthermore, the smoke may be harmful to health when inhaled by, for example, people.
US20120004825 describes a method for the operation of a combustion engine comprising an exhaust control system that includes an SCR catalytic converter.
US20110005199 describes a method to reduce emissions from a motor vehicle that has a combustion engine.